Means for delivery of flowable media, especially lubricants

ABSTRACT

A means for delivery of flowable media, especially of lubricants, with a pump ( 1 ) which can be driven by a motor and which forms a component of a line system is characterized in that at least one heating element ( 21 ) which can be activated by energy supply is located outside of the housing ( 3 ) of the pump ( 1 ) in a position which enables heat transfer to the housing ( 3 ).

The invention relates to a means for delivery of flowable media,especially of lubricants, with a pump which can be driven by a motor andwhich forms a component of a line system.

In known means of this type, under certain unfavorable operatingconditions there is the danger that malfunctions, for example a drop ofdelivery output, pump overload, or even its failure will occur. Thesedifficulties can occur especially when overly low oil temperatures occuras lubricating oils are being delivered in a lubricant circuit. Theseoperating states prevail for example during cold running phases ofcertain systems or occur in wind power plants under winter conditions,and these states can last over longer time intervals. The correspondingstrong increase of the viscosity of the lubricating oils to be deliveredleads at least to a reduction of the delivery output, resulting indanger to the assigned machinery system, or in less favorable casesleads to overloading or even failure of the pump; this in turn entailscorresponding subsequent damage to the pertinent system.

With respect to this prior art, the object of the invention is to makeavailable a means for delivering flowable media, especially lubricants,with operating reliability which is ensured even when very lowtemperatures of the line system and the medium to be delivered prevail.

As claimed in the invention this object is achieved by a means which hasthe features of claim 1 in its entirety.

According to the characterizing part of claim 1, the particularity ofthe invention consists in that heat transfer to the pump housing fromthe outside is provided. In this way, on the one hand the result is thatif necessary a direct temperature increase can take place in thecritical, i.e. fault-susceptible area of the line system, specificallydirectly on the pump. On the other hand, the heating of the pump housingleads to a corresponding temperature increase of the delivered medium;this causes a corresponding temperature increase of the entire pertinentline system, including an increase of a possible overly low oiltemperature in a lubricant circuit.

In especially advantageous exemplary embodiments there is at least oneheating element in the form of a self-regulating electrical resistanceelement with a positive temperature coefficient, for example in the formof a so-called PTC heating element. Commercially available PTC heatingelements consist of doped polycrystalline ceramic with barium titanateas the base material. These PTC elements ensure rapid heat-up, have goodself-regulation behavior and thus a long service life, since there is nodanger of overheating due to the self-regulating properties. The use ofsuch PTC elements is therefore also especially advantageous becausethese elements can automatically maintain a desired temperature level,without control means or temperature sensors being necessary.

Preferably the housing of the pump has more than one flat outside wallsection, to each of which one PTC element is assigned.

Preferably the arrangement here is made such that the PTC heatingelements are assigned to those outside wall sections of the housingwhich are spatially adjacent to the inside displacement elements of thepump. This piston arrangement leads to especially effective and promptheat-up in the desired region which is critical against insufficienttemperatures.

In exemplary embodiments in which on the pump housing the fluid inputand output which define the start and end of the inner pump flow pathwhich has the displacement elements are placed flush with one another onone end wall or rear wall of the pump housing, preferably on the sidewalls which join the end wall and the rear wall to one another, there isone PTC heating element each in this outside wall section which isplaced at the height of the fluid input and output. This yieldsespecially specific heat-up in the area of the inner flow path of thepump.

In advantageous exemplary embodiments, the carrier for the PTC heatingelements is an aluminum sheet which adjoins the pertinent outside wallsections for heat transfer, and adjoining the outer side of which arethe PTC heating elements made in a flat construction. This support ofthe PTC heating elements ensures especially good heat transfer to thepump housing.

In this connection the carrier can be made U-shaped and with U-legswhich run parallel to one another it can form one collar of the twoopposing outside wall sections of the pump housing at a time, on theoutside of each U leg there being one PTC heating element.

The PTC heating elements for their part can be held in contact with theU-legs by means of an enclosure which can be attached to the outside ofthe U-legs and which is made from highly heat-conductive metallicmaterial.

The efficiency of the means is especially good when the pump housing issurrounded with heat-insulating jacketing, leaving its pump shaft andfluid input and output exposed, so that heat losses to the vicinity arefor the most part prevented. This jacketing with which the housing isfor example cast round, prevents not only heat exit to the outside, butalso forms protective jacketing which prevents direct access to the PTCheating elements.

The invention is explained below in detail with reference to anexemplary embodiment shown in the drawings, in which

FIG. 1 shows a perspective oblique view of a pump intended for oneexemplary embodiment of the invention;

FIG. 2 shows a front view, looking at the end wall of the pump housing,its components surrounding the side walls being shown cutaway;

FIG. 3 shows a perspective oblique view of part of a carrier which formsthe collar of the side walls of the pump housing with PTC heatingelements located on its outside and their electrical connecting means;

FIGS. 4 and 5 shows a side view and a front view of the support fromFIG. 3;

FIG. 6 shows a bottom view drawn roughly in actual size of a metallicenclosure of a PTC heating element of flat construction held in it and

FIG. 7 shows a section according to line VII-VII from FIG. 6.

FIGS. 1 and 2 show a pump labelled 1 overall, with a pump housing 3which has a fluid input 9 provided with a connecting flange 7 on thefront end wall. Diametrically opposite on the rear wall which is notshown in the figures there is a corresponding fluid output which isflush with the fluid input 9. Within the flow path of the pump 1 betweenthe fluid input 9 and fluid output there is a gear pair which forms thedisplacement elements, i.e. the pump 1 is an outside gear pump with adrive shaft 11 which is located on the top of the housing. As is bestshown in FIG. 1, the pump housing 3 is surrounded with heat-insulatingjacketing 13, leaving exposed the areas of the fluid input 9, of thehousing top with the drive shaft 11, and of the area of the fluid outputwhich is not shown. In this connection it can be a cast or foamedjacket.

FIG. 2 shows the part of the jacket 13 which includes the side walls 15of the pump housing 3 which extend between the end wall 5 and the rearwall, in a vertically cut representation, its being apparent thatbetween the side walls 15 and the jacketing 13 there is a U-shapedcarrier.

FIGS. 3 to 5 show the carrier 17 in greater detail. The carrier 17 whichhas been shaped from aluminum sheet has two U-legs 19 which are intendedto make contact with the side walls 15 of the pump housing 3 and whichdefine planes which are parallel to one another. A PTC element unit 21which is shown only schematically in FIGS. 3 to 5 is attached to theoutside of each U-leg 19. FIGS. 6 and 7 show details of the PTC elementunits 21. Each of the element units 21 is provided with its own PTCelement 29 in the form of a flat cuboid. The latter is located in anenclosure 31 which is made in the manner of a round disk of metal withgood heat conductivity, provided with profiling. The enclosure 31 hascentral profiling 33 which on the bottom 35 of the enclosure 31 which isintended for contact with the pertinent U-leg 19 forms a receivingchannel 37 in which the PTC element 29 is fixed by a heat-resistantadhesive film strip 39, in the exemplary embodiment a Kapton® strip. Oneither side of the receiving channel 37 there are profilings 41 of lowheight with a round mounting hole 43 and an oblong hole 45 for forming ascrew connection between the enclosure 31 and the pertinent U leg 19.

Connecting wires 27 intended for power supply of the PTC element 29 areconnected in the manner conventional for PTC elements 29 to the flatmetal electrodes provided thereon. In the end area bordering the PTCelement 29 the connecting wires 27 are surrounded by a siliconeinsulating tube 47. Moreover the transition area between the end of theconnecting wires 27 provided with the insulating tube 47 can be sealedwith rubber in the area bordering the PTC element 29.

The enclosure 31 attached to the pertinent U-leg 19 of the carrier 17forms a heat conducting plate for transfer of the heat generated by thePTC element 29 to the aluminum sheet of the pertinent U-leg 19 which forits part adjoins the pertinent side wall 15 of the pump housing 3 as aheat transfer agent. This thermal coupling makes it possible using theself-regulating characteristic of the PTC heating element 29 to maintainthe desired temperature during changing operating states on the pumphousing 3 without the need for control electronics for this purpose.

The invention is explained above using the example of an outside gearpump. It goes without saying that the invention can be used likewise inpumps of a different design, for example for inside gear pumps, screwpumps, vane cell pumps, radial piston pumps or in pumps with a differentoperating principle. In any case it is advantageous to attach thepertinent PTC heating elements to the respective pump housing in aposition such that there is good thermal coupling to the pertinent innerdisplacement elements. While the invention is explained using oneexample in which two element units 21 with one contained PTC element 29each are used, it goes without saying that there could be a differentnumber of PTC elements 29 and that other designs different from the flatexecution can be used, for example PTC elements with a round orrectangular cartridge shape.

1. Means for delivery of flowable media, especially of lubricants, witha pump (1) which can be driven by a motor and which forms a component ofa line system, characterized in that at least one heating element (29)which can be activated by energy supply is located outside of thehousing (3) of the pump (1) in a position which enables heat transfer tothe housing (3).
 2. Means as claimed in claim 1, wherein at least oneheating element is a self-regulating electrical resistance element witha positive temperature coefficient, specifically a PTC heating element(29).
 3. Means as claimed in claim 2, wherein the housing (3) of thepump (1) has more than one flat outside wall section (15), to each ofwhich one PTC element (29) is assigned.
 4. Means as claimed in claim 3,wherein the PTC heating elements (29) are assigned those outside wallsections (15) of the housing (3)0 which are spatially adjacent to theinside displacement elements of the pump (1).
 5. Means as claimed inclaim 4, wherein the fluid input (9) and output which define the startand end of the inner flow path of the pump (1) which has thedisplacement elements are placed flush with one another on one end wall(5) or rear wall of the pump housing (3) and wherein on the side walls(15) which join the end wall (5) and the rear wall, there is one PTCheating element (29) each assigned to this outside wall section which isplaced at the height of the fluid input (9) and output.
 6. Means asclaimed in claim 3, wherein the carrier (17) for the PTC heatingelements (29) is an aluminum sheet which adjoins the pertinent outsidewall sections (15) for heat transfer, and adjoining the outer side ofwhich are the PTC heating elements (29) made in a flat construction. 7.Means as claimed in claim 6, wherein the carrier (17) is made U-shapedand with U-legs (19) which run parallel to one another it forms a collarof the two opposing outside wall sections (15) of the housing (3) of thepump (1) at a time and wherein on the outside of each U leg (19) thereis one PTC heating element (29).
 8. Means as claimed in claim 7, whereinthe U-legs (19) of the carrier (17) are connected by a crosspiece (23)which encloses the bottom part of the housing (3) of the pump (1), onthe outside of the crosspiece there being an electrical connecting means(25) for power supply of the PTC heating elements (29).
 9. Means asclaimed in claim 8, wherein the PTC heating elements (29) are held incontact with the U-legs (19) by means of an enclosure (31) which can beattached to the outside of the U-legs (19) and which is made from highlyheat-conductive metallic material.
 10. Means as claimed in claim 9,wherein the enclosures (31) of the PTC heating elements (29) adjoin theU-legs (19) over a large area.
 11. Means as claimed in claim 1, whereinthe housing (3) of the pump (1) is surrounded with heat-insulatingjacketing (13), leaving exposed its pump shaft (11) and its fluid input(9) and output.